My Squid and Bat, without the flares, but plenty of 'OIII dust'

[symmetal]

I previously posted my problems with flares on the RASA 11 here. I've since cured them by reducing the aperture on the exit side of the lens assembly by a few mm, but here I removed them using the 'Patch' tool in PS. What is evident is plenty of background 'dust' on the OIII which seems to be absent on other Squid images posted. I've squashed the OIII blacks as much as I can without removing any details in the squid. I'm assuming that using a 6nm OIII filter has let through more background than the 3nm filters commonly used, and the dust is not OIII emission, but broadband light reflected off the dust filtered by the wider OIII passband.

OIII starless image

On this target the OIII is stretched far more than the Ha and the dust would also be visible in the Ha if stretched enough, but at this point the Ha Bat would be clipped to white. Stretching the OIII by the same amount as the Ha reveals a black image apart from the star in the middle of the Squid.

Here's a modified HOO image and the blueish dust is evident thoughout giving a different representation compared to others. I could easily erase all the OIII dust around the Squid to make an image like many others, but as the dust is visible through the Squid it would be less accurate to showing what's present.

RASA 11 and ASI6200MM using Astronomik 6nm FastFR Ha and OIII filters. 3 hrs Ha and 7 hrs OIII. I tried capturing some SII but it turned out to be just a faint version of the Ha so didn't use it. Processed in PI and PS.

The unnamed blue patches to the left of the Squid and towards the bottom right are reflection nebula I assume, and not actual OIII emissions.

Another feature is the faint patch in the top right, to the right of the 3 stars in a row, which looks similar to some of the PGC galaxies labelled. It may be just a brighter patch of dust though.

Alan

[geeklee]

Excellent result Alan - plenty of depth in the Ha of the Bat and subtle detail throughout the squid.

10 hours ago, symmetal said:

but broadband light reflected off the dust filtered by the wider OIII passband.

Really interesting analysis of your OIII master and how you've brought that through into the HOO image to pepper it with additional OIII/dust/reflection elements throughout.

10 hours ago, symmetal said:

Another feature is the faint patch in the top right

Took me a minute to find this - top left?

[symmetal]

Thanks Lee, 

7 hours ago, geeklee said:

Took me a minute to find this - top left?

Oops, yes top left. 🤭 It's also visible on the OIII starless image, to the left of the similar looking PGC66550. Quite a few of the named PGC galaxies aren't visible in the final image so I'll check the images before the ...Xterminator processes were applied to see if they got erased from existence.

Alan

[symmetal]

Here are crops of the three areas I mentioned in the first post. Doing a quick search of other online images of the Squid these two 'nebula' don't appear to show any blue and the smaller one doesn't even appear at all, except as a bloated star. Not all specify the bandwidth of the OIII filter used. This is what made me think they are faint reflection nebula. Other opinions welcome. 😊

The 'OIII dust' does have a posterised look in places, as i think it's barely above the noise floor, and with the severe stretching applied there aren't enough 'bits' to represent it fully.

Here's the possible galaxy I noted. The one to the right of it does have a PGC designation.

I'll have to fire up Aladin to check further.

Alan